WHO pronounced in 1990 that it was its goal to develop a vaccine that was not only safe and stable under heat but also administered orally and supplied widely. The annual vaccine market reached 6 billion dollar scale recently, which was though, continued to be extended to reach 13 billion dollar scale in 2003. A vaccine development system today has some problems such as high price of production facilities and refrigerating equipments necessary for transportation and storage, difficulties in administration of a vaccine, reluctance of people to be injected, etc. So, an alternative vaccine needs to be developed to solve the above problems and especially for the children in underdeveloped countries who have not been favored with preventive inoculation. One of the promising studies to develop an alternative vaccine is a study on plant vaccine for oral administration prepared from transformed crops. An oral plant vaccine has a safety of a recombinant vaccine and easiness in vaccination (oral administration) as well as efficiency. The oral administration of a plant vaccine is just eating a transformed plant inserted with an antigen gene by a plant expression vector, which is as easy as eating food but still can induce immune response.
Korea advances an aging society. Aged men over 65 were 5.7% of total population in 1995 and 7% in 2001, which was a base line for being defined as an aging society by UN. With this tendency, an aged population will reach 15% of total population in 2020. Dementia patients in Korea are estimated to be at least 500,000, and 10,000 to 20,000 new patients are expected to be report annually. According to epidemiological survey, dementia patients are going to be developed by 1 person per 15 families in 2020. Patients with Alzheimer's disease take at least 60% of total dementia patients, which are about 300,000 people. Senile dementia, so called Alzheimer's disease, is a kind of degenerative nervous disease, which progresses for a long while beginning by causing troubles in recognition and going to destroy humanity. Thus, a passive approach to those patients cannot relieve social and economic burdens. An active approach to develop an agent for prevention and treatment of the disease is required.
All the dementia treatment medicines, which have been developed already or are under development, are nothing but symptom relievers, so that they cannot treat a cause of the disease directly but help functioning of cholinergic neurons. From the results of studies on Alzheimer's disease, the cause of the disease is believed to be an accumulation of beta-amyloid, a toxic protein, in brain, resulting in the death of neurons (Bacskai B J et al., 2001, Nature medicine 7:369-372; Schenk D. et al., 1999, Nature 400:173-177). So, one of the most effective ways to prevent and to treat a cause of Alzheimer's disease directly is to develop an agent inhibiting degeneration of nervous system by suppressing the generation of beta-amyloid and toxicity.
Beta-amyloid is a metabolite produced by a protease originated from APP (amyloid precursor protein), type I internal membrane protein, and is composed of 39˜43 peptides consisting of domains of a cell and a cell membrane. The beta-amyloid is formed during amyloidogenic metabolism by the action of β-secretase and γ-secretase, sorts of a protease. According to recent studies, a transformed mouse having Alzheimer type dementia caused by the expression of human beta-amyloid showed alleviation of behavior disorder resulted from the elimination of plaques accumulated in brain by the administration of beta-amyloid vaccine (Chen G. et al., 2000, Nature 408: 975-979; Janus C. et al., 2000, Nature 408:979-982; Morgan D. et al., 2000, Nature 408:982-985).
There has been no such attempt, in domestic and in the whole world, to express human beta-amyloid gene in a plant, so that there has been no report yet saying that a transformed plant, in which the gene was expressed, used as a vaccine for the elimination of beta-amyloid plaque.
One of the 4 major principal crops, potatoes have a perfect nutritive composition and has been widely cultivated to feed human through the world except intense cold and heat areas. Therefore, a successful development of a potato vaccine can create a huge steady demand.
In the meantime, tasty tomatoes are also cultivated and consumed world-widely. It is one of their merits to be eaten in the raw, which is one of the best benefits as an oral plant vaccine. Thus, a tomato has already been selected as a target farm product by many researchers. Both potatoes and tomatoes belong to Solanaceae. And it has also been reported that transformation is easy and the expression of an inserted foreign gene is stably completed in them (Chong D. K. X. et al., 1997, Transgenic Res. 6:289-296; Sandhu J. S. et al., 2000, Transgenic Res. 9:127-135).
Thus, in order to develop potatoes and tomatoes expressing beta-amyloid gene for the purpose of using them as oral plant vaccines for the prevention and the treatment of human Alzheimer type dementia, the present inventors inserted multiple beta-amyloid gene into Agrobacteria using an expression vector plasmid for transformation containing multiple beta-amyloid gene and cultured thereof together with potato leaves or tomato cotyledon tissues, and the inventors completed the invention by producing potato and tomato plants mass-expressing multiple beta-amyloid gene.